An Exploratory Proof of Concept Study to Assess the Pharmacokinetics/Pharmacodynamics (PK/PD) of Nemolizumab in Adult Participants With Chronic Pruritus of Unknown Origin (CPUO)

This study is to assess the PK/PD relationship of nemolizumab in adult participants with CPUO. The study will consist of a 2 to 4-week screening period, a 16-week treatment period, and an 8-week follow up period (12 weeks after last study drug injection). Participants will be randomized 4:1 to nemolizumab or placebo. Dosing will be adjusted according to participants body weight ( less than \[\<\] 90 kilograms \[kg\] versus \>= 90 kg). Participation in the study will last up to 28 weeks.